Definition of by-catch in English:

noun

Ices yesterday called for a ban on cod fishing in the North Sea, the Irish Sea and off the west coast of Scotland - and for a moratorium on fishing in areas where the species is caught as a by-catch - to rebuild fish stocks.

It had long been known that setting on tunas associated with logs produced high by-catches of other tuna species, sharks, mahi-mahi, wahoos, billfishes, and other large marine predators.

This is an ecologically minded practice for it prevents over fishing and eliminates by-catches.